To approach this from a slightly different perspective:
Ki, in Chinese chi or qi, in yoga "prana", in Hawaii "mana", all mean "breath". They translate literally that way. However, it would be more appropriate to think of it, not as breathing, but in the mythological or Biblical sense of the "breath of life".
Ki also can be translated as "life energy". It is inside all of us, around us in a field (your aura if you wish, your magnetic field if you prefer), and in and around all living things. Interestingly, it is also believed to exist in and around things that we would not necessarily think of as alive, like rocks or bodies of water.
Ki can be directed, just as you direct your arm to point at something or direct your legs to walk. You just have to learn how. It can also respond as a reflex, just as your arms and legs will respond without you needing to think about it.
Chinese medicine invented acupuncture, which uses needles to stimulate the flow of chi through the body in order to heal an illness or injury. They believe that chi flows through the body along meridians -- just as blood flows through veins, and electricity flows along our nerves. The main organ for our nervous system is the brain, of course. The main organ for our blood is the heart, or if you prefer, the marrow in our bones where blood is made. The main organ for chi is the Dam Dien, also spelled Tam Tien or Dandien. It is in the belly... I wish I could remember how the name translates right now -- it's something like Lake of Fire, as I recall.
In Tai Chi and Qi Gong, there is a very simple pose that is used to find the Dam Dien; the best way to find it is to simply stand quietly, and rest one hand on your belly, with your thumb just touching the navel. Then rest your other hand over the first, comfortably. Then breathe. Your hands are resting over the Dam Dien, and breathing into that place will help to fill it, and to stir the chi inside so that it flows more freely.
In Tai Chi, another beginning pose is described as "hugging a tree" or "holding a beach ball". The arms are elevated forward, at about chest height, and curved gently. Then breathe.
With practice you may be able to feel the energy fill the space inside your arms, like a large glowing ball of light.
The pose I just described is one that I have seen aikidoka use, in motion of course -- I've seen people roll with their arms in this position, I've seen them turn with an attacker's motion while flowing their arms around the "ball", and so on.
You can also move ki along the channels of your body, instead of creating a ball outside of you. Imagine that you are a tree. You can send roots into the earth, and breathe into them, and people will have a very difficult time pushing you over or lifting you. You can send it up into your arms like branches, and they will rest comfortably, without effort, but the people around you won't be able to bend them.
My soke told me that in Chinese calligraphy, the artist is meant to hold the pen with chi -- the grip is not tight, but no one can take the brush out of your hand while you do this. Soke handed me a ballpoint pen, and sure enough, his arm was shaking with the effort to take the pen out of my hand, but I felt like I was barely closing my fingertips around it.
Also, in theory, the letters that you write in that way would carry some of your ki with them, and be a little "powerful" so to speak.
I know that I push ki, or chi, when I give massage to people. I can use it to "hear" where they feel the most pain, and I can direct my hands to those spots; also, if I want, I can add my chi to theirs to help things flow properly, to loosen tight muscles, and so on. Most people feel this as a warmth or tingling.
I hope these descriptions help!